EP1726046A2 - Electric energy generating modules with a two-dimensional profile and method of fabricating the same - Google Patents

Abstract

An electric energy generating module is shaped to take on a desired two dimensional profile to match a non-flat surface or architectural element such as corrugated roofing. The module includes an electric energy generating film sealed between a top layer of encapsulant material and a bottom layer of encapsulant material. The type and quantity of the encapsulant materials are such that the shape of the encapsulant materials can be altered when a high temperature and/or pressure is applied to the module, but where the encapsulant materials provide a rigid structure around the electric energy generating film under ordinary (i.e., naturally occurring) temperature and pressure conditions. The module can therefore be shaped by applying a suitable pressure and/or a high temperature but, once placed under ordinary temperature and pressure conditions, the module has a rigid structure.

Description

ELECTRIC ENERGY GENERATING MODULES WITH A TWO- DIM ENSIONAL PROFILE AND M ETHOD OF FABRICATING THE SAM E

Reference data

Thisapplication claims priority of the USprovisional application US2004-553380 filed on March 16, 2004, the contentswhereof are hereby incorporated by reference.

Reld of the invention

The present invention relatesto the field of electric energy generating modules, such assolar cell modulesusing photovoltaic films More particularly, the present invention relatesto electric energy generating modulesthat are especially suitable for roofing and other architectural applications having non-flat surfaces The present invention further relatesto a method of fabricating such modules

Description of related art

Energy harvested from solar cell technology is being increasingly exploited asa valuable, renewable and generally ubiquitous resource. The solar cell industry continuesto grow asthe technology employed becomes more energy efficient and more inexpensive to produce. A solar or photovoltaic (FV) cell -- the terms" solar" and " photovoltaic" are used interchangeably herein - refersto a discrete element that converts light into electrical energy to produce a DC current and voltage. Typically, several such cellsare electrically connected in series to form a PV module (also sometimes referred to asa panel) to generate energy on a larger scale. Generally, a PV module includesthe solar cells and other ancillary parts, such as interconnections, contacts, structural elements, encapsulant materials, and protective devices such asdiodes. The structural (i.e., load carrying) element of a module isoften either a back layer substrate or a top layer superstrate. The latter must generally be transparent to transmit light to the PV cells A number of PV modules can be further connected together to form a larger array structure. The most common semiconductor material used in solar cellsis silicon- either in angle crystal, polycrystalline, or amorphousform. In addition to the variousformsof silicon, other semiconductor materials such asgallium arsenide, copper indium diselenide, and cadmium telluride are also used in solar cells Crystalline silicon solar cellsare commonly made from relatively thick (e.g., about 200 μm) silicon wafers sliced from a single crystal or polycrystalline ingot. However, more recently, it hasbecome common for modulesof much thinner solar cell filmsto be monolithically deposited onto low-cost substrates (such as glassor plastic) using well-known semiconductor manufacturing techniques Such thin filmsprovide several advantages, including easier and more cost-effective manufacturing and better suitability for mass production (although thisisgenerally at the expense of lower efficiency). In thin-film technology, laser processing can be used in between the variousdepos^'tion stepsto divide a large-area substrate into individual cells, and those cellscan be electrically connected to one another monolithically during the manufacturing process Amorphoussilicon, in particular, iswell-suited or use in thin film solar cells These PV cellsare typically made by depositing silicon using plasma-enhanced chemical vapor deposition of a reactive gassuch assilane with variousdopantsto form a P-l-N (or N-l-P) semiconductor structure having p-type, i-type (intrinsic), and n-type semiconductor layers

A PV module istypically sealed or encapsulated in some manner to protect the PV elements mechanically and against corrosion. The sealing also preventsthe infiltration of dust and water. The encapsulant covering the top surface of a solar cell module must be at least partly transparent to light so that at least some percentage of the desired wavelengthsof light reachesthe solar cells To provide a sturdier and less fragile construction, the bottom surface of a PV module (which does not need to transmit light to the solar cells) may consist of a rigid base layer formed of aluminum or another suitable material. PV modulesof this type are generally formed by laminating a thin film of solar cellsbetween the top transparent encapsulant and the bottom base layer, asdescribed for example in United States Patent Application No. 10/688,596 for a " Photovoltaic Product and Process of Fabrication thereof" , the contents of which are incorporated herein by virtue of this reference. Structurally rigid PV modules can also be formed by using a thick glass layer asa substrate or superstrate. Such rigid PV modules can be employed in architectural applications where the base layer is mounted to lie flat against a wall or roof surface. However, where the roof or wall does not have a flat surface (e.g., a roof with corrugated tiles), mounting the modulesonto the roof requiresthe use of a relatively elaborate mounting configuration underneath the modules and also must ensure that the intended function of the non-f lat surface (e.g., the removal of precipitation) is not compromised. Moreover, the use of flat PV modules on uneven surfaces is often detrimental to the aesthetic look of a building or other structure.

EP-A2-0874404 describes a solar cell module bent by application of a working pressure to give it the shape and rigidity required to use it in the same manner asordinary roof material. The module comprisesa photovoltaic layer with a rigid conductive substrate. Furthermore, a support member isstuck to the outside of the back surface in order to increase the mechanical strength of the module in order to realize the solar cell module which functions also as roof material. Therefore, the material of the support member must be selected among strong, rigid materialssatisfying the severe requirementsfor roof building elements Shaping and bending of the module isthusperformed by application of a substantial pressure only, requiring an expensive press equipment. A complicated layer arrangement must be provided in order to avoid high pressureson inner layersor small radiusof curvature which may damage the energy generating layer.

Furthermore, the module of EP-A2-0874404 comprises mutually connected discrete energy generating rectangular cells. The connection process istedious and expensive; there isa need for a continuous fabrication method. In addition, different cells are bent at different places and thusexposed to different amountsof sunlight. Aswill be appreciated, where the cellsare series-connected, the current in the resulting module is limited to the lowest current in any one cell. Asa result, the efficiency of the resulting module isgreatly reduced by high shading lossesin some cells

A similar solution isdescribed in US2001 /0045228. Again, the solar cell module described comprisesa rigid, for example stainless steel substrate. Aluminum strain holding plates are required to give shape in the areaswhere there is no solar cell. Bending requiresa high pressure and expensive equipment, and measures are required to prevent damage to the photovoltaic layer.

Another photovoltaic module in which a shape isgiven by a rigid substrate isdisclosed in USA1 -2003/0140959. Forming of the substrate isobtained through mechanical constraintsonly.

Solar cellscan also be fabricated on f lexible substrates, such as those made from polyimide or PET plastics, so that the resulting thin film PV module hasa flexible structure. An encapsulant material such asa fluoropolymer film (e.g) may then be used to seal the entire flexible PV module without significantly detracting from the module'sflexibility. One such encapsulant used in flexible PV modulesisthe Tefzel® film (produced by the DuPont Group of companies) applied together with ethylene vinyl acetate (EVA). Snce flexible PV filmscan be produced using roll-to-roll manufacturing techniques, they boast the potential for very low-cost production compared to filmsthat must be produced using batch techniques The resulting flexible modules are also lightweight and useful in certain typesof applications such asfor portable PV charger modules since they can be conveniently rolled into a tubular form to occupy less space when not in use. In addition, flexible PV modules are also capable of providing much better integration with structural elementsthat are not flat. Asa result, for example, f lexible PV modules have been used in roofing applications by mounting the moduleson top of roof tilesthat do not have a generally flat surface. Because of their flexibility, the flexible modules can be made to approximately assume the profile of a non flat surface, such as corrugated or undulating roof tiles (or of a similarly- shaped rigid base layer that is mounted onto those tiles). However, most flexible PV modules remain less durable and more fragile than their rigid counterparts making them less suitable for use in architectural applications where they are exposed to weather and/or other environmental conditions Furthermore, the shaping and mounting of each flexible PV module so that its profile matchesthe desired profile of the roofing elements remainsa relatively laborious process

In view of the above, there isclearly a need for a PV module that is better suited for applications (in particular, roofing or architectural applications) where there are non-flat surfaces with a two-dimensional profile, such as corrugated roofing.

SUM MARY OFTHE INVENTION:

The present invention relatesto an electric energy generating module (such asa PV module) that is particularly well-suited for mounting and integration in a location (such asthe faςade or roof of a building) where a non-flat physical surface iseither present or desired. This is accomplished by shaping the module so that the module takeson a desired two dimensional profile to match a non-flat surface or a non-flat architectural element. The present invention further relatesto a method of fabricating such an electric energy generating module. The invention also relatesto a module in which the efficiency lossesdue to shadesby profiled portionsof the module on other partsof the module are reduced.

Thus, in one aspect, the present invention provides an electric energy generating module comprising an electric energy generating film sealed between a top layer of encapsulant material and a bottom layer of encapsulant material. The type and quantity of the encapsulant materials are such that the shape of the encapsulant materials can be altered when at least one of a high temperature and a pressure is applied thereto, but where the encapsulant materials provide a rigid structure around the electric energy generating film under ordinary (i.e., naturally occurring) temperature and pressure conditions Through the application of pressure and/or a high temperature, the module isshaped to have and provide a desired two dimensional profile. Thereafter, once placed under ordinary temperature and pressure conditions (such asthose present outdoors) the module hasa rigid structure. The electric energy generating film comprisesa plurality of strip-shaped eel Is electrically connected with one another. The longitudinal direction of each strip-shaped cell extendsin parallel to a plane defining the two dimensional profile. Thus, shading on all serially connected strips is identical or at least comparable, and the efficiency of the module is not reduced by shading lossesthat arise when cellswith different currents are connected in series

In preferred embodiments, the electric energy generating film comprisesa PV film (for e.g., comprising an amorphoussilicon p-i-n semiconductor structure) and the top encapsulant material isat least partially transparent. The top encapsulant material isalso preferably UV resistant. The bottom encapsulant material may comprise the same material asthe top encapsulant material, but it may also be different.

In another aspect, the present invention provides a method of fabricating such an electric energy generating module. T e method comprisesproviding an electric energy generating film, a top layer of encapsulant material and a bottom layer of encapsulant material. At least one of a high temperature and a pressure are then applied to bond the electric energy generating film, the top layer of encapsulant material and the bottom layer of encapsulant material together asa bonded stack. Rjrthermore, at least one of a high temperature and a pressure are also applied to shape the bonded stack to provide the module with a desired two dimensional profile. In one preferred embodiment, the bonding comprisesapplying a temperature of between approximately 70 and 250^<Cand a pressure of between approximately 0.3 to 10 bar, and the shaping comprisesapplying a temperature of between approximately 70 and 250Oand a pressure of between approximately 0.01 to 1 bar. The shaping may be carried out immediately following the bonding or even simultaneously with the bonding. Again, bending/ shaping isperformed in such a manner that the longitudinal direction of the plurality of strip- shaped cell extendsin parallel to a plane defining the two dimensional profile.

BRIEF DESCRIPTION OF THE DRAWINGS The objectsand advantagesof the present invention will be better understood and more readily apparent when considered in conjunction with the following detailed description and accompanying drawings which illustrate, by way of example, preferred embodiments of the invention and in which: Rg. 1 isan exploded view of the various layers within a PV module, prior to a bonding step, in accordance with a preferred embodiment of the present invention;

Rg. 2 isa partial cross-sectional view taken along the line ll-ll in Rg. 1 showing one possible structure for the PV film of Rg.1 ; Rg. 3 isa high level diagram illustrating a bonding step for the

PV module of Rg. 1 ;

Rg. 4 isa high level diagram illustrating a profiling step for shaping the PV module so that it hasa desired two-dimensional profile;

Rg. 5 isa top perspective view of a profiled PV module in one embodiment;

Rgs 6A and 6B are side viewsof PV modules in other possible embodiments; and

Rg. 7 isan exploded view of the layerswithin a PV module, prior to a bonding step, in accordance with another embodiment of the present invention. Detailed description of preferred embodiments

In accordance with a preferred embodiment of the present invention, Rg. 1 isan exploded view showing the different films(i.e., layers) within a PV module 100, prior to the module undergoing a bonding step. While the present invention can also be applied to other types of electrical energy generating filmsand modules, it is particularly suited to the PV field, and asa result PV applications are referred to herein. This isin no way intended to limit the scope of the present invention to other suitable types of electrical energy generating filmsand modulessuch as, for example, a hybrid thermophotovoltaic (TPV) film.

As shown in Rg. 1 , PV module lOO isformed from a thin flexible PV film 110, a sheet of a top encapsulant material 150, and a sheet of a bottom encapsulant material 170. Although shown asflat (i.e., with a one-dimensional profile when viewed from the side), it will be appreciated that flexible PV film HO iscapable of adopting various 2-D profilesin the plane of the sheet. (In some cases, depending on the materials, structure and processesused even 3-D profiles can be adopted, though variationsin the third dimension will generally be much less pronounced than in the other two dimensions) Referring to Rg. 1 , PV film 110 includesa flexible substrate 120 onto which a PV semiconductor cell structure 130 isbuilt. Substrate 120 preferably comprisesa plastic foil such asa polyimide, PET (polyethylene terephtalate), or PEN (polyethylene naphthalate) sheet. Other flexible substrates can also be used, such as aluminium, insulator-metal compositesor fiber-enforced plastics Also, in the illustrated embodiment and as will be described in more detail below, each PV cell isshaped asa strip, and a plurality of thin conductors 140 and two thicker current collection busbars 145 run along top surface of PV cell structure 130. At least some anisotropic rigidity of the film 110 is given by the strips 130, by the conductors 140 and by the bars 145. A more important rigidity in the perpendicular direction will be given by the bending steps described below.

Top encapsulant material 150 istransparent to light 160 so that at least some percentage of the desired wavelengthsof light reaches PV film 110. Preferably, top encapsulant material 150 transmits a high percentage of incident light, for example at least 90%. Top encapsulant material 150 is also preferably UV-resistant (or UV-stabilized) so that its transparency, structural reliability, and resistance to corrosion do not significantly deteriorate when exposed to UV radiation for prolonged periods In addition, in some cases, UV radiation may cause the PV propertiesof the film to deteriorate, in which case it isalso important for top encapsulant material 150 to block any significant amount of such radiation from reaching the film. If top encapsulant material 150 is not naturally UV resistant, it may be given these UV resistant characteristics (i.e., UV-stabilized) by using additives or protective layersthat are either co-extruded or laminated onto the outer surface of material 150. Such additives or protective materials may include UV-absorbing materials or UV-stable polymers such asfluorinated polymers Bottom encapsulant material 170 may be opaque and need not necessarily be UV-resistant or UV-stabilized; however in some embodiments it may be most expedient to simply use the same material for both the top encapsulant and bottom encapsulant.

In accordance with the present invention, both the top and bottom encapsulant materials preferably comprise a thermoformable material, such asa thermoplastic polymer, that can be softened by the application of heat and that then re-hardens on cooling. For example, materials 150 and 170 may comprise PE (polyethylene), PET (polyethylene terephtalate), PEN (polyethylene naphthalate), PC (polycarbonate), PM MA (polymethyl methacrylate), EVA (Ethylene vinyl acetate), TPU (Thermoplastic polyurethane), ETFE (Ethylene tetrafluorethylene) or variouscombinationsof such materials Preferably, the softening temperature for the encapsulant materials 150 and 170 is between about 70 and 250^0. In another embodiment described further below, instead of (or in addition to) materials 150 and 170 being thermoformable, each of these materials may comprise an injection molding material.

For the sake of clarity, it is noted that Rg. 1 is not drawn to scale. However, the PV cell structure 130 may, for example, have a thicknessof between 0.1 and 20 μm, while substrate 120 may have a thicknessof between about 10 and 300 μm. For such PV films 110, the thicknessof the sheetsof materials 150 and 170 may correspondingly range from about 0.1 to 5 mm. It should also be noted that the thickness of the sheet of material 150 may be the same ast hat of material 170, but that these may also differ. Importantly, and asdiscussed in more detail below, the type and/or quantity of encapsulant materials 150 and 170 used in accordance with the present invention are such that the PV modules produced have a rigid and durable structure in ordinary conditions (i.e., naturally occurring temperatures and pressures), unlike the encapsulants conventionally used to seal flexible P film products ^'

A thin flexible PV film may use various different materialsand may have various different structures, asiswell known to one of ordinary skill in the art. Generally, a PV film employsa semiconductor to absorb photons above its energy band-gap, leading to the generation of charge carriers (electrons and holes). These charge carriers are then separated by an internal electricfield created by either a p-n or p-i-n junction within the semiconductor, or by a hetero-junction between the semiconductor and another material. The charge carriers are then collected by electrodes and used to generate a current in an outer circuit. The PV modulesof the present invention may generally use any type of thin PV film. In one illustrative embodiment, Rg. 2 showsa partial cross-sectional view of film 110 taken along the line ll-ll in Rg. 1. As shown, the PV cell structure 130 in Rg. 2 uses amorphous silicon (a-S), deposited to form a p-i-n PV element 133 comprising p-type (p), intrinsic (i), and n-type (n) layers located between a bottom electrode 132 and a transparent top electrode 138. The fabrication of such a PV cell structure iswell known and so is now only brief ly described. Prior to deposition of the amorphoussilicon layers,, the bottom electrode layer 132 of aluminum (Al) isformed by sputtering or other suitable technique. That layer isthen patterned (e.g., using a laser etching process) to separate the bottom electrodes of each cell. The n-type a-9 layer 134 isthen deposited over the bottom electrode layer by PECVD from a mixture of εilane and hydrogen together with a suitable dopant such as phosphine. Generally, no dopant isused during deposition of the intrinsic a-9 layer 135, while methane and diborane (or trimethylboron) may be added to the slane and hydrogen to provide the necessary doping for the subsequent p-type a-9 layer 136. Next, a transparent conductive oxide (TOO) top electrode layer 138 is deposited and then patterned to form void areas 139 to electrically isolate the top electrodesof neighboring cells The material of top electrodes 138 should allow a high transmission of photonsand suitable materialsinclude Indium-Tin-Oxide (ITO), Tin-Oxide (SnO₂), and Znc-Oxide (ZnO). On the other hand, bottom electrodes 132 may comprise any conductive material be it opaque (e.g., aluminum or silver) or a TOO as described above.

The above-described steps may be carried out using the single chamber roll-to-roll apparatusand method described in United States Patent Application Publication No. 2003/0172873A1 by Rscher et al., the entire contents of which are incorporated herein by virtue of this reference. In addition, to provide a seriesconnection between the parallel individual strip-shaped PV cells, a mechanical (or laser) scribe is used to etch a current-carrying grid pattern through the layers 138, 136, 135, 134, and (partially) 132. The etched areasare then filled with a conductive paste (e.g., a silver paste) to create thin conductors 140. In this manner, an electrical series connection is provided between the top electrode 138 and the bottom electrode 132 of neighboring cells

It will also be appreciated that apart from a single-junction p-i-n a-S PV cell structure, higher efficiency solar cell structures can be created using stacked tandem (p-i-n/p-i-n) or triple (p-i-n/p-i-n/p-i-n) junctions, or using cellsthat include a thicker i-type layer of microcrystalline silicon which may also be deposited by a PECVD process Furthermore, as already noted above, flexible thin PV films may also be based on other semiconductor materials such as polycrystalline silicon, microcrystalline silicon, thin film silicon, thin film tandem cells, copper indium gallium diselenide (QGS), ClSelements, cadmium telluride (CdTe), nano-crystalline dye-sensitized materials, or conductive polymers It will be appreciated that the semiconductor structure will generally differ depending on the material used. Referring now to Rg. 3, a lamination step for bonding thin flexible PV film 110 with the sheets of top encapsulant material 150 and bottom encapsulant material 170 isillustrated. Sheet 150, film 110, and sheet 170 are fed into a laminator 200 or other suitable device capable of bonding together the three sheets under a high temperature. In the illustrated embodiment, laminator 200 isa hot roll presswith two rotating drums210 and 220 that apply pressure at a temperature of between about 70 and 250^<Cto bond the sheetstogether and provide a bonded PV module stack 100'. In a preferred embodiment, the pressure applied by laminator 200 isfrom between about 0.3 bar to 10 bar (1 bar = 100 kPa), and in one specific example a pressure of 1 bar is used. The bonding process may exploit the self-adhesive properties of encapsulant materials 150 and 170, or additional layers of adhesive material (not shown), such as glue, silicon, or ethylene vinyl acetate, may be interposed between PV film 110 and each encapsulant sheet. Although laminator 200 appliesthe combination of both a pressure and a high temperature, in some embodimentsonly/primarily pressure or only/primarily high temperature can be used to effect the bonding, although the effectiveness of such techniqueswill generally depend on the type of encapsulant materials 150 and 170 being used. It will nevertheless be appreάated'that whatever combination of temperature and pressure are applied, the imposed conditionswill not be conditionsthat occur naturally, i.e., a combination of temperature and/or pressure that module 100 would otherwise be exposed to. The bonding step may occur in a variety of different manners

In one embodiment, the bonding step occurs as an entirely batch process using a flat pressthat bondstogether individual flat sectionsof film 110, top encapsulant 150, and bottom encapsulant 170 to form the bonded stack 100' for a angle PV module (preferably so that an overlap of encapsulant surroundsthe PV film on all sides). Thistechnique may be preferred if an adhesive layer (such as an EVA layer) isalso used to help create the bonded stack 100'. Alternatively, a roll batch process may be used in which sheetsof film 110, top encapsulant 150, and bottom encapsulant 170 are fed into a roll press (such as laminator 200 in Rg. 3) from three individual rolls Asanother alternative, continuousfilms corresponding to a plurality of PV modulesof film 110, top encapsulant 150, and bottom encapsulant 170 may be fed into a roll pressfrom three individual rolls, and cut to the desired length after lamination or after shaping. It is preferred that the encapsulant materials overlap each side of the PV film to provide edge sealing, and thisisposa^'ble using either of the first two techniquesdescribed above. However, for the continuous filmsin the third technique, when the continuous laminated material is cut, the PV film will be exposed at the cut edge and therefore will be susceptible to infiltration and/or degradation. In thiscase, an additional step to seal the cut edge may be carried out by reheating the severed bonded stack and welding the existing thermoplastic materialsin the stack around the exposed edge to seal it. If necessary or desired, additional thermoformable material can also be added to the bonded stack when sealing the cut/exposed edge.

In some embodiments, it may also be desirable to carry out the bonding step in a vacuum to help prevent any air being incorporated into the sealed bonded stack 100'. Rjrthermore, while the top surface of a bonded PV module stack 100' may be simply f lat, that surface may also be textured in a manner that alters reflection properties, avoids glare, improves light trapping, and/or improvesthe aesthetic look of the module. Thistexture may be applied by ua^'ng a suitable surface structure on the lamination press/rolls used to bond together the layers

In accordance with the present invention, after the different sheetsof the PV module have been bonded together, the bonded stack 100' isfurther shaped by the application of pressure (preferably together with a high temperature) to provide a PV module 100 with a desired two- dimensional profile (i.e., a two-dimensional outline as seen from the side). In the illustrated embodiment of Rg. 4, a profiling device 300 includes complementary mold sections 310 and 320 operating at a high temperature to mechanically force module 100 into a desired profile shape. In a preferred embodiment, the pressure applied by device 300 variesfrom about 0.01 to 1 bar, and in one specific embodiment the pressure applied is 0.05 bar. The temperature in device 300 corresponds to the softening temperatures of the thermoformable encapsulant materials 150 and 170, which as noted above may be f rom between 70 and 250°C. In alternative embodiments, the profiling step may be carried out by fixing the bonded stack 100' in the frame of a molding device, heating the stack, and then applying a vacuum through holesin two complementary mold sectionsso that air pressure compressesthe mold sectionsagainst the bonded stack 100' so that the latter takeson the shape of those mold sections Uke the bonding step, the profiling step may be carried out as a batch process (asillust rated), or a continuous roll process may be used. Furthermore, the profiling step may be carried out immediately after the bonding step, possibly within the same device (i.e., laminator 200 and profiling device 300 may be combined), since the bonded PV module stack 100' generally does not require cooling prior to undergoing the profiling step. Asa further alternative, both the bonding and the profiling step may occur at the same time, as single process step. The above approaches are preferred if encapsulant materials 150 and 170 comprise a thermoplastic polymer that degrades chemically when repeatedly heated and cooled or especially if encapsulant materials 150 and 170 comprise a thermosetting material which can only be heated and cured once.

As another alternative, instead of bonding and profiling as described above, a profiled PV module 100 can be realized using injection molding techniques In thiscase, PV film 110 is placed in a profiled injection mold (not shown), and an encapsulant resin material (with the transparency and UV resistant properties mentioned above) is injected to embed the module in the desired profile shape. Suitable examples of injection molding encapsulantsinclude PET (polyethylene terephtalate), PC (polycarbonate), PP (polypropylene), PA (polyamide), ABS(acrylo nit rile / butadiene / styrene) or various combinationsof such materials

Re-hardening of the encapsulant material after shaping is preferably performed by cooling, or letting the module return to ambient temperature condition. However, depending on the materials used, hardening may be improved, initiated or accelerated using chemical agentsor ultra-violet light for example.

Once the profiling step has completed and PV module 100 has cooled, a rigid, strong, durable and still relatively lightweight PV module is provided even though no rigid plate or support member (such as aluminum or glass base) forms part of the module. As will be appreciated, it isan important aspect of the present invention that the type and quantity of encapsulant materialsused are sufficient to provide PV module 100 with such a rigid and durable structure once the module has cooled and isused under ordinary conditions (i.e., naturally occurring temperaturesand pressures). Thisdiffersfrom the encapsulation of existing thin film flexible PV moduleswhere the type and/or quantity of encapsulant used allow the modulesto retain their flexible nature under ordinary conditions In one exemplary embodiment of the present invention, the overall thicknessof PV module 100 isabout 2 mm which providesa strong, rigid, and yet lightweight structure.

The shape of the profile of PV module 100 can be corrugated (i.e., with alternating ridges and grooves), standing seam (i.e., interlocking), or any other desired non-flat (i.e., 2-D profile) shape required for a given application. In the embodiment of Rg. 4, PV module 100 iscorrugated with an approximately sinusoidal profile. A more detailed top perspective view of such a PV module isshown in Rg. 5. Alternate PV module profiles are also exemplarily shown in Rgs 6A and 6B. More specifically, Rg. 6A shows a side view of a PV corrugated module 100A with a corrugated trapezoidal profile, while Rg. 6B showsa a^'de view of a PV corrugated module 100B with a profile suitable for providing a standing seam effect so that neighboring PV modules can interlock with one another. As shown, in the specific embodiment of Rg. 6B, even though PV module 100B has a 2-D profile, the profile of PV film 110 inside module lOOB is nonethelessflat (i.e., film 110 has a 1-D profile) in thiscase. Typically, the top and bottom surfacesof the PV modules are otherwise uniform, in that a cross-section of the module in a plane parallel to that of the 2-D profile will share the same 2-D profile. However, thisis not necessary and may not be the case where sections acting asfixing points, border sections, or for making electrical contacts are included in the PV module.

Furthermore, a three-dimensional texture may be provided in the top-encapsulant layer, for example by using mold sections310 and possibly 320 with a textured surface. The texture may define micro-optical elements, for example micro-lenses, for improving convergence of light onto photovoltaic active portions of the film 110 and for deviating light away from the non-active portionsof the film (such asthe interconnection areas 139 and 140 and areas covered with additional current collecting finger grids). In addition or alternatively, the texture may improve the optical appearance of the module, and/or might reduce unwanted glare of the module surface.

Aswill be appreciated, where the PV cellsin PV module 100 are series-connected, the current in the PV module is limited to the lowest current in any one PV cell. Asa result, as shown in Rg. 5, the longitudinal axisxl of the strip-shaped cellsand the thin conductors 140 that monolithically provide the electrical series connections between neighboring cellsare preferably oriented in parallel to a plane x;z defining the 2-D profile of the module (i.e., the plane of the drawing). This ensures that no PV cell is located entirely (or predominantly) along a groove or valley within the 2-D profile where the cell may be exposed to only minimal sunlight which would significantly limit the current conducted through the PV module asa whole. Instead, with the cell orientation of Rg. 5, no shading lossesoccur (other than pure geometrical losses) since each cell will generally be exposed to the same amount of sunlight and therefore generate the same amount of current. Serial-connection of the stripswill thus be possible without reducing the resulting current over the cells Similarly, although the cell orientation is not shown in Rgs 6A and 6B, where the cellsand series-connectionsfor modules 100A and 100B are strip shaped, these again are preferably oriented in parallel to a plane defining the 2-D profile of the module. Of course, if the PV cellsin module 100 are electrically connected in a different manner, a different cell orientation may be preferable.

As also shown in Rg. 5, PV module 100 may have two contact openings 146 formed through the encapsulant material to connect electrical wires 148 to each current collection bus bar 145 in PV film 110. For illustration purposes, contact openings 146 are shown as having been made through the top surface of PV module 100 in Rg. 5. However, more typically, the contact portionswill be formed via an opening formed through the encapsulant from the bottom surface of the module. Contact openings 146 are preferably formed after the bonding and profiling steps are complete, in the manner described in United Sates Patent Application 10/688,596 for a " Photovoltaic Product and Processof Fabrication thereof" , the contents of which are incorporated herein by reference. Once the necessary connections have been made, openings 146 may be sealed for protection purposes Aswill be appreciated, by connecting wires 148 to PV module 100 the module may be connected with other PV modules as part of a PV array and/or to an external electrical circuit. Alternatively, instead of attaching wires 148, openings 146 may simply enable electrical connection of PV module 100 directly to an underlying PV junction box. As noted, after they have been shaped, the PV modulesare rigid, strong, and durable. Asa result, the modulesare better able to withstand exposure to adverse weather and other environmental conditionscompared to most conventional flexible PV film products At the same time, by taking on a desired 2-D profile shape, the PV modules of the present invention can be more fully integrated into a desired application since they provide a better structural fit. For these reasons, the PV modulesof the present invention are well-adapted to be mounted onto existing architectural surfaces (such as corrugated or profiled roofing or facade elements) that are not flat. Moreover, in some cases, the PV modulesof the present invention may entirely replace existing architectural elements (such as roof tilesor facade elements), so that the PV modules provide both the PV function and the desired architectural/structural function. More generally, the modulesof the present invention are well-suited for use in any location having a non-flat surface.

The profiles of PV modules l OO may correspond to the size and shape of existing materials already used and standardized within the construction and roofing industry, for example 76 mm or 18 mm corrugated roof tiles In addition, each PV module can be mounted onto (or can replace) one or several standardized architectural units For example, a single PV module 100 may be produced with a 1 x 2 meter surface size and could be used to cover (or replace) several roofing tiles With existing PV manufacturing processes, such a module would be able to produce a peak PV power of about 50-300 Watts at about 12 to 300 Volts Optionally, the size of the module could be increased, e.g., to 2 x 10 meters, to cover an entire roof section or the whole length of a facade. Alternatively, the surface area of a PV module may be reduced to correspond to the size of a single individual roof tile, e.g., 30 x 50 cm. Mounting of a PV module 100 -- either to or as an architectural element - may occur in any conventional manner. For example, a module 100 may be fixed to another element or a surface using clips, using screws through mounting holesdrilled through the profile, or using any other fastening technique. In some cases, it may be desirable to provide an air gap beneath a profiled PV module to help cool the PV film and improve its efficiency. Multiple PV modules l OO may also be welded or glued together to form a larger sealed section for a roof or facade. A PV module 100 may further be combined with a thermal insulation layer (e.g., polyurethane foam) beneath the module. Such an insulation layer is preferably applied along the entire bottom surface of the profiled PV module, for example by applying the foam to that surface by extrusion. Such an insulation layer may additionally improve and stabilize the mechanical and structural propertiesof the profiled PV module. In particular, a back-insulated profiled module isparticularly advantageous in conjunction with the use of amorphousalicon asa PV material, since the temperature coefficient of the power output by such a module is relatively small.

While the invention has been described in conjunction with specific embodiments, it isevident that numerous alternatives, modifications, and variationswill be apparent to those skilled in the art in light of the foregoing description. For example, in one possible variation, Rg. 7 illustratesthe layersused (prior to bonding and profiling) in a PV module 400. Asshown, module 400 includesa PV film 410 including a PV cell structure 430 fabricated on a relatively thick superstrate 450 comprising, for example, PET (polyethylene terephtalate) and a sheet of bottom encapsulant material 470. In thisembodiment, superstrate 450 actsas both an insulating base on which PV cell structure 430 is fabricated aswell asthe top encapsulant layer in the subsequent bonding step. In this manner, superstrate 450 should possessthe transparency and UV resistant characteristics previously described for top encapsulant layer 150. It may also be noted that superstrate 450 may have a relatively large thickness so that the resulting PV film 410 is not flexible under ordinary (i.e., naturally occurring) temperatures Alternatively, the thicknessof superstrate 450 may be relatively small but the thickness of the sheet of bottom encapsulant material 470 may be correspondingly increased, in which case PV film 410 may still be flexible. Rjrthermore, it will be appreciated that, in thisembodiment, the base electrode first deposited onto superstrate 450 should comprise a TOO and, if a p-i-n configuration is used for cells in PV cell structure 430, p-type, i-type, and n-types layers are then sequentially deposited above the TOO electrode layer. Rnally, although in Rg. 7 the superstrate 450 isshown as having a larger surface area than PV cell structure 430, it may not be practical to fabricate PV film 410 in this manner. If so, to ensure that, the edges of PV cell structure 430 are sufficiently protected and covered by encapsulant material after bonding, a larger bottom encapsulant sheet 470 may be used and/or additional encapsulant material may be added after the PV film 410 and the sheet of bottom encapsulant 470 have been initially bonded together. The resulting bonded stack can then be profiled in the manner described above. Several modules may be assembled together, after shaping but preferably before mounting on a roof, in order to extend the width and/ or the length or the resulting photovoltaic element. Bectrical connections between neighboring modulesare preferably accomplished without any wire, by overlapping or contacting the busbars 145 in order to provide the desired serial or parallel connections Assembly of the different modulesishowever made in such a manner asto guarantee identical or similar sunshine amount on mutually serially connected cellswhen the assembled photovoltaic element is mounted. More specifically, in an embodiment where the module is intended for use on or asa corrugated or profiled roofing element, the plane x;z defining the two dimensional profile of the module may extend in an upward direction substantially parallel to the ridge or edge of the roof. In thiscase, the strips 130 preferably extend along an horizontal direction parallel to this ridge or edge.

If, on the other hand, the plane x; z defining the two dimensional profile extendsin an upward direction perpendicular to the ridge or edge of the roofing, the strips 130 preferably extend in an upward direction, perpendicular to said ridge or edge. The module may also be used asa profiled or corrugated substantially vertical facade element. In thiscase, if the plane (x; z) defining the two dimensional profile is horizontal when said module is mounted, the stripswill preferably extend horizontally. If on the other side the plane isvertical, the stripswill preferably extend in an upward direction.

Claims

Qaims

1. An electric energy generating module (100) comprising: an electric energy generating photovoltaic (PV) film (110) sealed between a top layer (150) of at least partially transparent encapsulant material and a bottom layer (170) of encapsulant material, wherein the type and quantity of the encapsulant materials are such that the shape of the module can be altered when at least one of a high temperature or a pressure is applied thereto but wherein the encapsulant materials provide a rigid structure around the electric energy generating film (110) under ordinary temperature and pressure conditions, wherein the electric energy generating film comprises a plurality of strip-shaped cells (130) electrically connected with one another, wherein the module isshaped to provide a desired two dimensional profile, and wherein the longitudinal direction (x1 ) of each strip-shaped cell (130) extendsin parallel to a plane (x;z) defining said two dimensional profile.

2. , The module of claim 1 , wherein said striped shaped .cells (130) are connected in seriesto one another.

3. The module of one of the claims 1 or 2, wherein the type and quantity of the encapsulant materials and of the other layers are such that the shape of the module can be permanently altered by application of the following steps: softening of the encapsulant materialsby application of a high temperature, application of a pressure to the module (100) in order to obtain the desired shape, hardening of the encapsulant materials

4. The module of claim 3, wherein the type and quantity of the encapsulant materialsare such that the shape of the module can be altered by the application of a temperature of between approximately 70 and 250°Cand a pressure of between approximately 0.01 to 1 bar.

5. The module of one of the claims3 to 4, wherein the type and quantity of the materialsused in at least one layer of the module are such that the shape of the module cannot be permanently altered under normal temperature conditionswithout cracking, even if a pressure isapplied temporarily thereto.

6. The module of one of the claims 1 to 5, wherein the electric energy generating film (110) comprisesa substrate (120) flexible under ordinary temperature and pressure conditions

7. The module of claim 6, wherein the substrate (120) of the electric energy generating film (110) comprises at least one of the following materials: polyimide, PET (polyethylene terephtalate), or PEN (polyethylene naphthalate), aluminium, insulator-metal compositesor fiber-enforced material.

8. The module of one of the claims 1 to 7, wherein, in accordance with the two dimensional profile of the module, the electric energy generating film (110) within the module (100) is not flat.

9. The module of one of the claims 1 to 8, wherein the electric energy generating film (110) comprisesan amorphousa^'licon semiconductor structure, a microcrystalline silicon, a thin film silicon, a CIS element, a CdTe element and/or a thin film tandem cell.

10. The module of one of the claims 1 to 9, wherein the electric energy generating film (110), the top encapsulant material (150), and the bottom encapsulant material (170) have been bonded together to provide a stack with a flat profile, prior to the module having been shaped to provide a two dimensional profile.

11. The module of one of the claims l to 10, wherein the electric energy generating film (110), the top encapsulant material (150), and the bottom encapsulant material (170) have been sealed together in a continuous laminating process, prior to the module having been shaped and cut at the desired length.

12. The module of one of the claims l to 11 wherein the module (100) isshaped using an injection molding process and the top and bottom encapsulant materialscomprise a resin suitable for injection during said process

13. The module of one of the claims l to 12 wherein the top encapsulant material comprises at least one of the following materials: PE (polyethylene), PET (polyethylene terephtalate), PEN (polyethylene naphthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), EVA (Ethylene vinyl acetate), TPU (Thermoplastic polyurethane), ETFE (Ethylene tetrafluorethylene).

14. The module of claim 13 wherein the bottom encapsulant material comprisesthe same material asthe top encapsulant material.

15. The module of one of the claims l to 14, wherein the two dimensional profile of the module(100) correspondsto the non-flat profile of an architectural unit or surface to enable the module to be mounted onto said architectural unit or surface or to replace one or more of said architectural units

16. The module of claim 15, wherein the two dimensional profile of the module correspondsto the profile of a corrugated or profiled roofing or facade element.

17. The module of claim 16, wherein the two dimenaonal profile of the module correspondsto the profile of a corrugated or profiled roofing, wherein said module comprises at least one strip (130) intended to extend along a direction substantially parallel to the ridge or edge of said roofing when said module is mounted, and wherein said plane (x; z) defining said two dimensional profile extendsin an upward direction substantially parallel to said ridge or edge when said module is mounted.

18. The module of claim 16, wherein the two dimensional profile of the module correspondsto the profile of a corrugated or profiled facade element, wherein said module comprises at least one strip (130) intended to extend along a direction substantially horizontal when said module is mounted, and wherein said plane (x; z) defining said two dimensional profile extendsin direction substantially horizontal when said module is mounted.

19. The module of one of the claims l to 15, wherein the two dimensional profile of the module correspondsto the profile of a corrugated or profiled roofing, wherein said module comprises at least one strip (130) intended to extend in an upward direction when the module is mounted, and wherein said plane (x; z) defining said two dimensional profile extendsin an upward direction substantially perpendicular to said ridge or edge when said module is mounted.

20. The module of claim 16, wherein the two dimensional profile of the module correspondsto the profile of a corrugated or profiled facade element, wherein said module comprises at least one strip (130) intended to extend along a direction substantially vertical when said module is mounted, and wherein said plane (x; z) defining said two dimensional profile extendsin direction substantially vertical when said module is mounted.

21. The module of one of the claims l to 20, wherein the top layer of encapsulant material also comprisesa superstrate for the electric energy generating film.

22. The module of one of the claims l to 21 , further comprising a thermal insulation layer applied to a bottom surface of the module after the module has been shaped.

23. The module of one of the claims 1 to 22, further comprising a three-dimensional texture in said top-encapsulant layer designed so asto improve convergence of light on to PV active portionsof the module.

24. A method of fabricating an electric energy generating module

(100) comprising: providing an electric energy generating film (110) comprising a plurality of strip-shaped cells (130) electrically connected with one another, a top layer of encapsulant material (150) and a bottom layer of encapsulant material (170); applying at least one of a high temperature and a pressure to bond the electric energy generating film, the top layer of encapsulant material and the bottom layer of encapsulant material together asa bonded stack; and maintaining or applying a high temperature to melt / soften said encapsulant material, and applying a pressure to shape the bonded stack to provide the module with a desired two dimensional profile, wherein the type and quantity of the encapsulant materials provided are such that the shape of the module can be altered when at least one of a high temperature and a pressure isapplied thereto but wherein the encapsulant materials (150, 170) provide a rigid structure around the electric energy generating film (110) under ordinary temperature and pressure conditions, and wherein the longitudinal direction (x1) of each strip-shaped cell extendsin parallel to a plane (x;z) defining said two dimensional profile.

25. The method of claim 24 wherein the bonding comprises applying both a high temperature and a pressure.

26. The method of claim 25 wherein the bonding comprises applying a temperature of between approximately 70 and 250°Cand a pressure of between approximately 0.3 to 10 bar and wherein the shaping comprisesapplying a temperature of between approximately 70 and 250°C and a pressure of between approximately 0.01 to 1 bar.

27. The method of one of the claims24 to 26, wherein the shaping iscarried out immediately following the bonding.

28. The method of one of the claims24 to 27, wherein the shaping is carried out simultaneously with the bonding.

29. The method of one of the claims24 to 28, wherein the shaping comprises using an injection molding process and the top and bottom encapsulant materialscomprise a resin suitable for being injected during said process

30. The method of one of the claims24 to 29, said high temperature being sufficient for melting said encapsulant materials without damaging said electric energy generating film (110), said method comprising a step of releasing said temperature for re-hardening the encapsulant materials after shaping.

31. The method of one of the claims24 to 30, further comprising a step of applying a three-dimensional surface texture to said top- encapsulant layer.